1. Field of the Invention
This invention relates generally to medical device systems and, more particularly, to medical device systems and methods capable of assessing and managing extreme events related to epilepsy.
2. Description of the Related Art
Generalized tonic-clonic status epilepticus, referred to herein as Convulsive Status Epilepticus (CSE) is a neurological emergency with an estimated incidence of about 20 out of 100,000 patients and is generally considered an extreme event. CSE is also associated with a mortality rate between 3% and 40% depending on etiology, age, status type, and status duration. CSE, in particular, requires immediate, aggressive, and effective treatment to stop seizure activity, to prevent neuronal damage, systemic complications and the possibility of death. Most investigations on prognosis of status epilepticus (SE) have focused on mortality, and some research suggests that outcome basically depends on the etiological and biological background but also that the earlier the therapeutic intervention the higher the probability of controlling it. Additionally, non-convulsive status epilepticus (nCSE), while not a medical emergency of the magnitude of CSE, it is also an extreme event as nevertheless it increases the risk of bodily injury and neurologic deficits such as permanent potentially severe impairment in memory.
CSE and nCSE are defined based on the duration of a single seizure and its variations or on the lack of recovery of certain neurologic functions to their inter-ictal (baseline) levels in the context of closely spaced seizures. The focus on seizure duration or frequency or on level of consciousness or of awareness to determine if a patient is in status epilepticus has important limitations, since signals or indices from others systems such as cardio-vascular, respiratory, endocrine and metabolic which are also adversely impacted by the seizures and which directly contribute to the increased (compared to the non-epileptic population) morbidity and mortality of patients with epilepsy are disregarded. The state of the art views and treats Status Epilepticus narrowly and ineffectively. Embodiments of this invention takes a system's approach by quantifying the impact of seizures on bodily functions (e.g., neurologic, cardiovascular) to determine the probability they are harbinger of extreme events (e.g., status epilepticus) and to prevent them from occurring, or if they are extreme, to provide early treatment and/or warning to avert serious neurological and medical sequelae or even fatal outcomes.
Sudden Unexpected Death in Epilepsy, or “SUDEP,” another extreme event, is a phenomenon in which a patent with epilepsy dies unexpectedly and without an apparent, outstanding cause, that is, the death is unexplained since autopsy results are unrevealing. One of the main risk factors for SUDEP is the lack of seizure control with first line drugs prescribed alone or in any safe combination and dosage. Whether or not the first in a chain of ultimately fatal events leading to SUDEP is a seizure, the defining event is likely to be either cardiac (e.g., ventricular fibrillation or asystole) or respiratory (e.g., apnea) or both. Currently, the monitoring, detection, prediction and prevention of SUDEP are underdeveloped and markedly limited in breadth and depth of scope, limitations which embodiments of this invention address.
CSE and nCSE alter autonomic nervous system function and SUDEP may be caused by autonomic dysfunction. Since brain/neurological activity such as electrical activity, whether normal or abnormal, and autonomic functions (e.g., cardiovascular activity, respiration, etc.), referred to herein as body signals (from which body data may be derived), are functionally tightly coupled; monitoring these body signal provides valuable information. This is the first invention to utilize not only neurologic, autonomic, metabolic, endocrine and tissue stress marker signals but do so in a multi-variant adaptive manner to optimize sensitivity and specificity of detection of extreme epileptic events (e.g., CSE, SUDEP), and, more importantly to anticipate them.